1. Field of the Invention
The present invention relates to a telemetering intracranial pressure transducer of a small size which can be embedded below the skin of the head of a body to be tested without damaging a dura under the skull of the test body for allowing precise remote measurement of the intracranial pressure within the skull over a continued period of time.
2. Description of the Prior Art
The head of a human body to be tested is of supreme importance for the life and social life thereof. The internal pressure within the skull of the head may be varied due to external causes such as blows to the head, traffic accidents and the like, or internal causes such as intracerebral hemorrhage, encephaloma and the like. When the brain is lightly affected by such a variation in the internal pressure in the skull, the body suffers from a headache, dizziness, vomiting or the like. When the brain is severely influenced by an intracranial pressure change, there results a severe headache, consciousness loss, anaerosis or the like.
It has been practiced in the fields of cerebro-surgery and cerebro and neuro-surgery to detect the internal pressure in a skull as a method of studying causes of the foregoing symptoms and maintaining life.
One means for picking up information as to the internal pressure in the skull of a body comprises an electric pressure transducer for detecting the intracranial pressure through a hole formed in the skull. The transducer produces an electrical signal indicative of the intracranial pressure, and hence is capable of precise measurement and reliable operation. However, the electric pressure transducer needs a lead wire extending from the head of the test body to a monitoring device for indicating measurements. The patient is therefore subjected to limited activities by the lead wire. With the lead wire extending out from below the skin of the head, the lead wire has a tendency to cause the portion of the head to which the lead wire is attached to get infected with bacteria during a long period of measurement.
As a means for measuring an intracranial pressure wirelessly, there has been proposed a system in which a device with a coil or a capacitor having a variable constant is bodily embedded in the skull, and a search coil is brought from the exterior into close proximity with the coil or capacitor, whereupon the inductance of the coil or the capacitance of the capacitor is detected to measure the internal pressure in the skull. This measuring system however fails to gain a required degree of precision of measurement due to the influence of the head skin acting as a source of noises, and also fails to detect dynamic signals from within the skull.